1. Field of the Invention
The present invention relates to an electric vehicle or a hybrid vehicle which is respectively equipped with an electric motor or an engine and an electric motor as a driving source or driving sources for the traveling of the vehicle. More particularly, the present invention concerns a vehicle-use battery cooling system for cooling batteries which are mounted as a driving source for an electric motor.
2. Description of the Related Art
In recent years, electric vehicles which travel by means of the driving force of an electric motor, instead of an engine which obtains its driving force by burning fuel such as gasoline, are becoming widespread. Such an electric vehicle is equipped with an electric motor and rechargeable batteries as a driving source for driving the electric motor, and travels as the electric motor is driven by electric power supplied from the batteries. The electric vehicle is capable of traveling continually as the batteries are recharged at predetermined timings.
In the batteries mounted in the electric vehicle, heat generation occurs not only during charging but also during discharging for supplying power to the electric motor. In addition, if the temperature rises, not only does the performance of the batteries decline, but also the life of the batteries declines appreciably. On the other hand, if the temperature drops, outputs of the batteries naturally decline, and the charging efficiency also declines.
For this reason, some electric vehicles are provided with cooling and heating apparatuses for cooling or heating batteries. In the electric vehicle equipped with this heating and cooling apparatus for the batteries, the batteries are accommodated in a predetermined accommodating space, and the accommodating space is maintained within a predetermined temperature range by the cooling and heating apparatus.
For example, as vehicle-use battery cooling systems adapted to maintain the batteries within a predetermined temperature range, the following systems are known: one in which the battery temperature is detected and the cooling air from the air conditioner is supplied to the battery accommodating space as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 7-73906, one in which the air conditioned during the temperature rise of the batteries is introduced to cool the batteries as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-262144, and one in which the air volume of the blower is increased when the battery temperature has exceeded a predetermined level as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 8-40088.
In the cooling and heating apparatuses for batteries disclosed in these publications, the temperature of the batteries or the temperature of the battery accommodating space is detected, and on the basis of the detected result cold air or warm air is forcibly supplied from the air conditioner for effecting the air conditioning of the vehicle compartment.
However, since these cooling and heating apparatuses effect the cooling and the like of the batteries by forcibly producing cold air or warm air irrespective of the state of air conditioning of the vehicle compartment, the comfortable feature of the vehicle compartment is impaired.
Meanwhile, the vehicle compartment interior is maintained within a temperature range of 20.degree. C.-30.degree. C. by the air conditioner, and the temperature for using the batteries in an optimum condition is higher than this vehicle compartment temperature. As the air in the vehicle compartment is supplied to the battery accommodating chamber as necessary, it is possible to effect the cooling of the batteries efficiently without stopping the air conditioning of the vehicle compartment. Consequently, it becomes possible to efficiently cool the batteries while maintaining the air-conditioned state of the vehicle compartment by means of the air conditioner.
However, there are cases where the temperature of the batteries becomes high depending on the condition of use, and if the air used for cooling the batteries enters the vehicle compartment, the temperature of the vehicle compartment interior is increased, and the cooling load of the air conditioner becomes higher, or the temperature of the vehicle compartment interior is locally increased, thereby causing an increase in the heat loss, impairment of the comfortable feature of the vehicle compartment, and the like.